It has been suggested to use movement of the human eye to monitor involuntary conditions, such as a person's wakefulness or drowsiness. For example, U.S. Pat. No. 3,863,243 discloses a device that sounds an alarm to warn a person using the device that they are beginning to fall asleep. The device includes a frame similar to a set of eyeglasses onto which is mounted an optical fiber and a photocell that are directed towards the user's eye when the frame is worn. The photocell detects the intensity of light reflected off of the user's eye, i.e., either by the eyelid when the eye is closed or the eye surface when the eye is open. A timer distinguishes between regular blinks, and an extended time period during which the eye is closed, i.e., a time period that may indicate that the person is falling asleep. When a threshold time elapses, an alarm is sounded to notify and/or wake the user.
Another device is the Alertness Monitor by MTI Research Inc., which may be mounted on safety glasses, and emits a continuous infrared beam of light along the axis of the eyelid at a strategic position where the beam cannot be broken by the eyelashes except during an eyeblink, giving it the ability to measure eyeblink frequency. Other devices, such as those disclosed in U.S. Pat. Nos. 5,469,143 and 4,359,724, directly engage the eyelid or eyebrow of a user to detect movement of the eye and activate an alarm when a drowsiness condition is detected. Such devices may include mechanical devices, e.g., a mechanical arm, or a piezoelectric film against the eyelid.
It has been suggested to mount cameras or other devices to a dashboard, roof, or other location in a vehicle to monitor a driver's awareness. Such devices, however, require the user to maintain constant eye contact with the camera. In addition, they do not monitor eyelid movement if the user turns his head sideways or downwards, turns around, exits the vehicle, if the user moves around rapidly, or if the camera moves relative to the individual. Further, such cameras may violate privacy and/or have problems seeing through eyeglasses, sunglasses, or even contact lenses, and may not operate effectively in sunlight.